A Dutch psychiatrist is calling for an independent organisation to oversee the review of asylum seekers on Nauru.

Australia and the United Nations High Commissioner for Refugees have recently announced that they will review the cases of some of the 248 people remaining on Nauru, who were denied refugee status.

But, Maarten Dormaar, who spent four months on Nauru assessing the mental health of asylum seekers, says he is cynical about the process.

He says if it's carried out by unofficial interpreters selected by Australian immigration officials, as it was the first time, there is little hope for those who have now been in detention for more than two years.

"These people need legal advice. These are very simple people. They have never gone through such a kind of process of being interrogated and interviewed and their life depends on it. So, they really need kind of an advocator, a lawyer who is present and who can help them to bring their story forward."

Mr Dormaar also says that the mental health of the asylum seekers is continuing to deteriorate and that the more than 90 children in the camps will suffer long term mental health issues as a result of being detained.